Thermoplastic copolyetherester elastomers, such as those disclosed in U.S. Pat. No. 3,766,146, are known for their generally good physical properties and their outstanding processing characteristics. Unfortunately, these copolyetheresters are deficient in scuff resistance which reduces their suitability in certain applications. Moreover, lower hardness grades of copolyetheresters lack toughness; for instance, their tensile and tear strengths are often lower than desired.
Japanese patent application publication No. 44-20477 describes elastic polymers which are prepared by polycondensation of about equimolar amounts of a diimide-diacid and a poly(alkylene oxide) glycol. This disclosure exemplifies the use of diimide-polyether copolymers in fibers. As is known, the drawing which forms a part of the spinning process results in orientation and increased crystallinity within a polymer. In molding operations, it is not possible to take advantage of the property improvements resulting from drawing. It has been found that the polymers of Japanese No. 44-20477 are generally unsatisfactory for use in molded goods because of poor stress-strain properties, low softening points and poor solvent resistance.
A new class of polymers containing diimide-diacid segments and polyether segments has been found. The polymers are thermoplastic elastomers which have outstanding scuff resistance, low permanent set and excellent stress-strain properties even at low hardnesses.